This invention pertains to a method and apparatus for the hyperthermia destruction of tumors or the like. More particularly, it relates to such a method and apparatus which is noninvasive, and which employs bidirectionally radiated and focused electromagnetic energy generated by a special-purpose antenna constructed in accordance with the teachings of a prior U.S. patent of mine--identified below.
Current methods for the treatment of tumors in humans and animals include surgery, chemotherapy, and hyperthermia techniques such as X-ray irradiation, ultrasound, nuclear radiography, and electromagnetometry using convection. Numerous problems, however, are associated with all of these methods. For example, surgical removal of a tumor is highly invasive, and has all the attendant risks of any surgery, which are particularly enhanced with seriously ill patients. In addition, certain tumors are inoperable due to their position and formation in the body. Chemotherapy and hyperthermia techniques using X-ray irradiation, ultrasound, nuclear radiography, and electromagnetometry are all non-specific--generally exposing the entire body, and thereby generating a host of serious side effects.
A general object, therefore, of the present invention is to provide a unique, noncontacting, in vivo hyperthermia method and apparatus for destroying tumor cells and the like in a localized, circumscribed area, without destruction of surrounding tissue.
More specifically, an object of the invention is to provide such a method and apparatus that employs heat generated by an antenna which focuses and radiates two beams of electromagnetic energy bidirectionally so as to converge upon a pair of spaced focal regions, one of which embraces a tumor site inside a body, and the other which embraces a "simulated tumor" positioned outside the body.
Study of biological tissues indicates rather large differences in dielectric constants among various tissues. For example, skin and bone each has a dielectric constant of about [9], brain tissue a dielectric constant of about [34], muscle about [52], blood about [72], and cerebrospinal fluid a dielectric constant of about [80]. It is also established that tumor cells exhibit an approximate dielectric constant of [36], whereas normal cells surrounding tumors, which are typically fat cells, exhibit an approximate dielectric constant of [15].
As disclosed in my U.S. Pat. No. 4,234,844, issued Nov. 18, 1980, entitled "Electromagnetic Noncontacting Measuring Apparatus", it is possible to monitor such differing electrical parameters by generating and focusing electromagnetic energy at a pair of electrically related, spaced-apart focal points. According to the teachings of this patent, a bidirectional microwave antenna, made in accordance both with this patent, and with my companion U.S. Pat. No. 4,318,108, (issued Mar. 2, 1982, and entitled "Bidirectionally Focusing Antenna") may be aimed to place one of its focal points, or regions, adjacent a preselected interrogation site inside a body wherein certain electrical characteristics are to be observed. By using a receiver located adjacent the other focal point, or region, it is possible, by monitoring voltage, current and phase conditions at the receiver, to determine related electrical conditions at the interrogation site.
In the present invention, such an antenna is used to focus electromagnetic radiation bidirectionally toward a pair of spaced-apart focal regions that are disposed symmetrically with respect to the antenna. One of the focal regions is placed inside a patient's body to embrace a tumor site, while the other focal region is positioned to embrace an external simulated tumor having substantially the same dielectric constant as the "real" tumor. The simulated tumor is suspended in a tank containing a liquid medium with, as near as it is possible to attain, the same temperature and dielectric constant as the healthy tissue surrounding the real tumor. The temperature of the simulated tumor is then monitored to indicate the temperature of the "real" tumor. Once a preselected temperature, known to cause cell death, is reached at the simulated tumor, that temperature is maintained over a predetermined period of time until cell death within the "real" tumor site has occurred.
In the operation just described, destruction of a tumor is accomplished without physical invasion of the body. Further, due to localization of electromagnetic radiation, destruction of the tumor is accomplished without concomitant destruction of neighboring normal tissue having substantially lower dielectric constants than tumors--a condition important to proper application of this invention.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.